1. Field of the Invention
The present invention relates to a motor control system which uses a numerical controller that performs both control of a motor and control of a display device.
2. Description of the Related Art
When a numerical controller of a machine tool transmits commands to a plurality of motors to control each of the motors, the motors are driven by a plurality of amplifiers depending on the number and the types of motors. In Japanese Patent Application Laid-Open No. 2008-242728, regarding such a numerical controller, a first mode in which the same number of serial bus control circuits as the number of amplifiers are provided and the amplifiers and the serial bus control circuits are connected by serial buses such as optical cables so that each of motors is separately controlled by the corresponding amplifier, and a second mode in which a single serial bus control circuit is provided, the serial bus control circuit and amplifiers are connected in series, and a numerical controller and the amplifiers are connected by serial buses are disclosed.
In addition, a technique is also known in which a display device which displays various types of information of a numerical controller is provided separately from the body of the numerical controller, and display data to be displayed on the display device is transmitted by a different serial communication channel from serial buses for motor control to display the display data on the display device. Furthermore, a technique is also known in which an external input/output interface such as a keyboard or a USB for operating a numerical controller is provided in a display device, and data from the external input/output interface is subjected to data communication by the same serial communication channel as that for display data.
FIG. 5 is a schematic view illustrating a connection state of the numerical controller, the motors, and the display device in the related art.
In a numerical controller 110, a serial bus control circuit 112 and a display device serial communication channel control circuit 116 are provided. A display device 120 is connected to the display device serial communication channel control circuit 116 by a serial bus 160. In addition, a first amplifier 131 is connected to the serial bus control circuit 112 by a serial bus 150. A first motor 141 is connected to the first amplifier 131 so that the first motor 141 is controlled by the first amplifier 131. The first amplifier 131 and a second amplifier 132 are connected to each other also by the serial bus 150. A second motor 142 is connected to the second amplifier 132 so that the second motor 142 is controlled by the second amplifier 132.
Although the data amount of a motor command transmitted to each of the amplifiers 131 and 132 by the numerical controller 110 is small, in order to realize the highly accurate control at high speed, communication needs to be performed at a high frequency at a constant interval.
FIG. 6 is a view illustrating the data configuration of the motor command in the related art.
The data of the motor command initially includes a start code which indicates the start of the data and subsequently includes a command for each of the motors such as a first motor command, a second motor command, . . . , an N-th motor command. Each of the amplifiers which receive the data extracts the command for the motor connected to the corresponding amplifier from the received data, and thereafter transmits the received data to the amplifier in the next stage (subsequent stage). In the same manner, the amplifier in the next stage also extracts the command for the motor connected to the corresponding amplifier from the received data, and thereafter transmits the received data to the amplifier in the next stage. Although not illustrated in FIG. 6, a point where the motor is not present has empty data as the data of the motor command.
FIG. 7 is a view illustrating the configuration of communication data of position information from each of the amplifiers to the numerical controller in the related art.
The communication data from each of the amplifiers initially includes a start code which indicates the start of the data and subsequently includes position information from each of the motors such as first motor position information, second motor position information, . . . , N-th motor position information. Each of the amplifiers which receive the data adds the position information of the motor connected thereto to the data and transmits the resultant data to the amplifier in the next stage (preceding stage). In the same manner, the amplifier in the next stage also adds the position information of the motor connected thereto to the data and transmits the resultant data to the amplifier in the further next stage (preceding stage).
FIG. 8 is a view illustrating the configuration of communication data for the display device in the related art.
The communication data initially includes SYNC data for communication synchronization and subsequently includes the display data. In a case where there is no communicating data, the SYNC data for communication synchronization is transmitted. In addition to the display data, input/output data (I/O data) is also transmitted.
Although not illustrated, the input/output data or data (HMI data) of a key input or the like from a keyboard is transmitted from the display device to the numerical controller.
In the above-described technique disclosed in Japanese Patent Application Laid-Open No. 2008-242728, the technique of connecting the numerical controller and the amplifiers of the motors by the serial buses is disclosed, but a technique related to the display device is not disclosed.
In the related art illustrated in FIG. 5, the technique related to the communication data for the display device 120 is also disclosed. However, the display data for the display device 120 is transmitted by using a serial bus in a different protocol from that of the serial bus for the motor control. Therefore, the number of serial buses and the number of serial bus control circuits 112 are increased, and thus the technique may become complex and cost may also increase.